Tapered spring leaf suspension for driver tandem axle assembly

ABSTRACT

This specification discloses a suspension for a motor vehicle or trailer. The suspension comprises multiple tapered leaf springs fixed near their centers to an axle. At tareweight, the leaves are separated from each other near their ends. At full load, the leaves are compressed together near their ends. This provides a changing spring rate corresponding to variance of load. The arm of one leaf is rigid to horizontal compression, resisting acceleration and braking loads.

United States Patent [72] Inventor Donald J. McGee Troy, Mich. [21]Appl. No 690,164 [22] Filed Dec. 13, 1967 [45] Patented May 25, 1971[73] Assignee Dura Corporation [54] TAPERED SPRING LEAF SUSPENSION FORDRIVER TANDEM AXLE ASSEMBLY 13 Claims, 5 Drawing Figs.

[52] U.S. Cl 180/22, 267/38, 267/40, 267/54, 280/104.5, 280/124 [51]Int. Cl 860g 5/00, B60g 19/02 [50] Field of Search 280/124, 104.5 (B),104.5; 267/36, 38, 40, 47,54; 180/22, 23, 24

[56] References Cited UNITED STATES PATENTS 2,054,305 9/1936 Stilwell267/54X 2,458,816 l/1949 Woods 280/124 2,626,144 1/1953 Stephen 280/124X2,655,388 10/1953 Nabors..... 280/l04.5 2,907,579 10/1959 Masser280/104.5 3,024,038 3/1962 Butler 280/l04.5(B) 3,053,527 9/1962 Hallam267/47 3,157,412 11/1964 Frazier..... 280/104.5(B) 3,365,190 1/1968Usalis 267/54 Primary Examiner-A. Harry Levy Attorney-David A. Maxon O Vo o PATENTEU HAYES |97| SHEET 2 UF 2 MOE INVENTOR Don 4L0 J 6 5 BY flaw!G. film ,3

ATTORNEY TAPERED SPRING LEAF SUSPENSION FOR DRIVER TANDEM AXLE ASSEMBLYThis invention relates generally to suspensions for trucks and trailers.More specifically, this invention relates to a suspension for a truck ortailer embodying a multitapered leaf spring having one leaf secured on abracket fixed to the frame, and another leaf seated against a cam fixedto the truck frame at one end and free from contact from another camfixed to the frame at its other end until the truck is loaded.

ln truck and trailer suspensions, it is desirable to have a suspensionsystem capable of providing a different spring rate for loaded andunloaded conditions of a truck or trailer. This desirable characteristicof having a different spring rage for loaded and unloaded conditionsmust be considered together with the necessity for minimum levels ofstrength in means for suspending such vehicles. it is also desirablethat the spring rate vary in a smooth continuous manner as increasedload is placed upon a vehicle.

Accordingly, it is an object of this invention to provide a suspensionsystem for truck or trailer having a smooth, continuously varying springrate as load is increased on the vehi cle.

It is another object of this invention to provide a suspension systemfor a truck or.trailer that takes up increased load by providing anextra arm of a spring to take such extra load in a smooth, continuouslyincreasing proportion as the load is increased on a vehicle.

It is another object of this invention to provide means for smoothly,continuously varying spring rates and increasing structuralload-carrying capability with a truck or trailer in combination with aspring and vertical load-carrying member also absorbing acceleration andbrake loads on the suspension system.

It is another object of this invention to provide a suspension systemfor a truck or trailer with variable spring rates that is light andinexpensive to build and maintain.

These and other objects of this invention are accomplished by providinga suspension system with a multitapered leaf spring combination. Thiscombination comprises at least two tapered leaf springs fixedly attachedto one another near their centers. The bottom leaf spring is coiled atone end to form a female cylindrically shaped bearing surface. This isjournaled on a bracket fixedly attached to the frame of the vehicle. Thejournaled arm of the spring absorbs acceleration and brake loads on thesuspension system. The topmost tapered leaf spring has an arm at its endmost distant from the journaling of the aforesaid leaf spring that is incontact with a cam member fixed to the frame of the vehicle. The otherarm of the topmost spring, at its end near the toward means of theaforesaid lower spring, is initially spaced at a vertical distance froma cam surface provided by a bracket fixed to the frame. While thevehicle is still in an unloaded condition, the arm of the lower spring,at its end furtherest from the aforesaid journaling on the other arm ofthe lower spring, is separated at its extreme end by a vertical-distancefrom the nearest arm of the topmost spring. As the vehicle is loaded,the topmost and bottommost springs are pressed towards each other andhave a greater area of contact with one another. The free arms of thetop and bottom springs move towards their nearest cam surfaces fixed tothe frame of the vehicle. When the vehicle is fully loaded, both arms ofboth springs are each carrying a significant portion of the load andeach contribute a significant portion toward the spring rate of thecombination.

Other objects of this invention will appear in the following descriptionand appended claims, referring to the accompanying drawings forming apart of this specification.

On the drawings:

FlG. l is a partial transverse sectional view of a tapered leaf springused in the preferred embodiment of this invention;

FIG. 2 is a transverse sectional view of a combination of tapered leafsprings used in the preferred embodiment of this invention;

FIG. 3 is a side view of the preferred embodiment of this invention:

FIG. 4-is a cross-sectional view taken along lines 4-4 of FIG. 3; and

FIG. Sis a cross-sectional view of the apparatus shown in FIG. 3 takenalong lines 5-5 of FIG. 3.

Before explaining the present invention in detail, it is to beunderstood that the invention is not limited ,in its application to thedetails in construction and arrangement of parts illustrated in theaccompanying drawings since the invention is capable of otherembodiments and of being practiced or carried out in various ways. Alsoit is to be understood that phraseology and terminology employed hereinare for the purpose of description and not of limitation.

As shown on the drawings:

FlG. l is a partial view of a tapered leaf spring used in the preferredembodiment of this invention. The spring 10 is shown in a flat oruncambered position. The middle portion 14 of the spring is flat. Theleft arm portion of the spring has a gentle slope on its underside l6tapering to a narrower thickness at its forward end. Immediatelyadjacent and aft of the bottom flat portion 14 is a portion 18 that hasa steeper angle of narrowing thickness than the slope 1'6. Aft andadjacent to the bottom surface 18 is the bottom surface 20 whichcontinues to slope at a less steep angle than the slope of surface 18.

ln FIG. 2 there is shown a combination of two tapered leaf springs suchas the leaf spring 10 shown in FIG. 1. These springs are cambered intopartial ellipses. The bottom spring 22 is attached at its center portion24 to the center portion 26 of a top spring 28. This is accomplished bymeans of shims or liners 30 placed on the top and bottom surfaces of thesprings 22 and 28, and a nut and bolt assembly 32.

The forward end 34 of the bottom spring 22 is rolled into a cylindricalshape. Inserted into this cylindrical shape is a cylindrical bushing orhearing 36. The forward arm 37 of the spring 22 bears a significantportion of the vertical load on the suspension combination in both theloaded and unloaded condition of the vehicle to which it is attached, aswell as the brunt of acceleration and braking loads applied to thesuspension system. This is referred to as a Bartuska in the art.

The aft portion 38 of the bottom spring 22 is curved upwardly from themiddle near shim 30. Its end 40 has a subsequent slight downturn and isseparated at a distance from the end 42 of the aft portion 44 of the topspring 28 when the spring combination 46 is placed in a vehicle in arelatively unloaded condition. Thus, when the spring combination 46 isin a vehicle in a relatively unloaded condition, the aft portion 38 ofthe lower spring 22 does not carry any of the load applied to thesuspension system.

The forward portion 48 of the top most spring 28 is curved upwardly fromthe middle portion 26 of the top spring 28. Its forwardmost end 50 isbent downwardly and forward of the Bartuskalike end 34 of the bottomspring. Should the forward portion 37 of the bottom spring 22 fail, thehooked end 50 of the topmost spring 28 provides a reserve safety meansfor catching hold of the bracket, to which the Bartuska 34 is attached,to support the load released by a broken spring portion 37.

In the normal relatively unloaded condition of the vehicle, in which thespring system 46 is illustrated in FIG. 2, the top surface 52 of theforward portion 48 of the top spring 28 is separated at a distance fromany contact with the frame of the vehicle or structural member attachedto it. Thus when the vehicle is in an unloaded condition, no loads arecarried by the forward portion 48 of the topmost spring 28 of the springsystem 46.

The aft portion 44 of the top spring 28 is curved upwardly from themiddle portion 26 of the spring 28. The end 42 of the aft portion 44 hasa surface 54. This surface is in direct contact with a cam surfacebracketed to the frame of the vehicle. Throughout both the loaded andunloaded conditions of such a vehicle, the upper aft portion 44 supportsvertical load applied to the suspension. The distance between the bottomsurface 56 of the topmost spring 28 and the topmost surface 58 of thebottom spring aft portion 38 is the same as the distance separating thetop surface 52 of the forward portion 48 of the topmost spring'a'nd acam surface of a bracket that comes into contact with surface 52 whenthe vehicle is sufficiently loaded. These corresponding differences arereduced at a similar rate as increased load is placed upon the vehicle.When a predetermined level of load is reached, the topmost surface 52 ofthe forward arm 58 of the top spring 28 begins to bear a portion of thevertical load on the vehicle. At the same time, the aft portion 38 ofthe bottom spring 22 also begins to bear a portion of this verticalload.

In FIG. 3 there is shown a side view of the preferred embodiment of thisinvention. In it, two spring assemblies are shown of the type shown inFIG. 1. This is an application to a tandem axle. For both axles, similarspring assemblies 62 forward and 64 aft are used. They are attached attheir central portions 66 and 68 to axles 70 and 72 respectively. Theseaxles are driven by drive train members 71 and 73, respectively. Thesprings are secured to the axle by means of U-bolts 74 and 76respectively, shims 78 and 80 respectively, spring seats 82 and 84respectively, and axle clamps 85 and 86 respectively. v

The forward arm portion 88 of the lower spring 90 of for' ward springcombination 62 is secured to a Bartuskalike securing means showngenerally at 92 and illustrated in further detail in FIG. 4.

The securing assembly 92 comprises a spring hanger bracket 94 which isrigidly secured to the frame 96 of the vehicle by means of bolts 98. Acompression bolt 100 is inserted in the bracket 94 and is pressedagainst a rubber bushing that is cylindrically shaped and coaxial withthe compression bolt 100. A bolt 104 has a parallel noncoincident axisand rotates within the compression bolt 100. By turning the bolt 104,the position of the spring assembly 62 can be changed in order toprovide precise location of the axle to which it is secured with respectto means driving this axle. An assembly 112 similar to the securingmeans 92 secures the forward arm portion 114 of the lower spring 116 ofthe aft spring assembly 64.

A walking beam 120 has a forward cam surface 122 and aft cam surface 124for engaging the upper surface of the aft portions 126 and 128respectively of upper springs I30 and 132 respectively of forward springassembly 62 and aft spring assembly 64 respectively. The walking beam120 has rubber rollers 134 and 136 respectively at its forward and aftends below cam surfaces 122 and 124 respectively. These lower rubberrollers 134 and 136 provide a lower limit for travel of springassemblies 62 and 64 respectively. They stop the aft portions 138 and140 respectively of lower spring members 90 and l 16 respectively. 7

The walking beam 120 is joumaled to the frame of the vehicle 96 by meansof a securing means shown in detail in FIG. 5. This securing means 166comprises a bolt 170 secured by a steel cap 162 and" rubber bushing 168passing through the frame 172 and the walking beam portion 120. Thisassembly is secured by bolts to the frame.

It can be appreciated that in the preferred embodiment of thisinvention, with walking beam 120 contacting the rear portion of theforward and rear spring assemblies 62 and 64, the difference between theangles of the axes of means (pinion gears) driving the wells on thefore-and-aft shafts 70 and 72 is minimized during braking andacceleration.

It can also be appreciated from the foregoing description that the usesof multiple tapered leaf spring assemblies as shown is such that theforward arm of the lower spring in each spring assembly is secured tothe frame of the vehicle in such a manner that precise location of theaxles to which the springs are attached can be adjusted. Also, brakingand acceleration loads will be applied to and carried by the forwardarms of the lower spring members. Thus, the forward arms of the lowersprings in both spring assemblies provide a dual function of carrying asignificant portion of the vertical load as well as the acceleration andbraking loads applied to the suspension systems. This will account for aconsiderable saving in weight.

It can also be appreciated that in the operation of a vehicle embodyingthe above-described described suspension, that the spring rate of thesuspension varies as increased load is placed upon the vehicle. ltcanalso be seen that the strength of the members carrying vertical load ona suspension is increased in correspondence with increased load beingplaced upon the vehicle. This is accomplished by adding additional armsof leaf springs into a structural load-carrying position as the vehicleis loaded from a relatively unladen to a fully laden condition. This isdone in a smooth and continuous manner, and results in the upper andlower spring portions of each spring combination coming into fullcontact with one and other as the vehicle is fully loaded.

The wheels of the vehicle are held in a ground engaging position whentransversing bumps by the walking beam member maintaining contact withthe aft portions of the tandem suspension. Similar action of the walkingbeam reduces pinion angle on interaxle drive due to acceleration orbreaking windup. In an alternative embodiment of this invention, thewalking beam may actually be another spring having a spring rate havingthe same order of magnitude as the aforementioned tapered leaf springs.'There may be variations in the taper of the springs such as havingsymmetrical tapers and having tapers on both sides of the spring. Inanother alternative embodiment of the present invention, one of thetapered leaf springs may be replaced by a combination of a composite,multiple leaf spring.

I claim:

1. In a motor vehicle suspension, the improvements comprising:

a driven axle; v

a frame for the vehicle;

an upper tapered spring leaf having a thickness along a substantiallength thereof at least 30 percent greater than the thickness alignanother substantial length thereof;

a lower tapered spring leaf having a thickness along a substantiallength thereof at least 30 percent greater than the thickness alonganother substantial length thereof;

means securing said spring leaves to the axle near the centers of saidspring leaves;

a bracket attached to said frame forwardly of said axle;

a flange on said bracket;

a camming surface on the underside of said flange;

said upper spring leaf and said lower spring leaf being shaped andsecured with respect to each other comprising means separating theforward portion of said upper spring leaf at a distance from saidcamming surface when said vehicle is relatively unladen;

means securing the forward end of said lower spring leaf on saidbracket;

a second camming surface attached to said frame and in contact with therear portion of said upper spring leaf;

said upper spring leaf and said lower spring leaf being shaped andsecured with respect to each other comprising means separating the rearportion of said lower spring leaf at a distance from said upper springleaf when the vehicle is in a relatively unladen condition; and

said upper spring leaf and said lower spring leaf being shaped andsecured with respect to each other, and said second camming surfacetransmitting to the rear portion of said upper spring leaf a portion ofthe structural load on the suspension when the vehicle is more fullyladen comprising means reducing said last-mentioned distance and causingthe forward upper portion of the upper spring leaf and said rear portionof the lower spring leaf bear a portion of the structural load on thesuspension when the vehicle is more fully laden;

the forward portion of the upper spring leaf and the portion of thelower spring leaf and the portion of the lower spring leaf between saidbracket and axle being of a taper with increasing thickness rearwardlyfrom said bracket to said axle.

1. In a motor vehicle suspension, the improvements comprising: a drivenaxle; a frame for the vehicle; an upper tapered spring leaf having athickness along a substantial length thereof at least 30 percent greaterthan the thickness align another substantial length thereof; a lowertapered spring leaf having a thickness along a substantial lengththereof at least 30 percent greater than the thickness along anothersubstantial length thereof; means securing said spring leaves to theaxle near the centers of said spring leaves; a bracket attached to saidframe forwardly of said axle; a flange on saiD bracket; a cammingsurface on the underside of said flange; said upper spring leaf and saidlower spring leaf being shaped and secured with respect to each othercomprising means separating the forward portion of said upper springleaf at a distance from said camming surface when said vehicle isrelatively unladen; means securing the forward end of said lower springleaf on said bracket; a second camming surface attached to said frameand in contact with the rear portion of said upper spring leaf; saidupper spring leaf and said lower spring leaf being shaped and securedwith respect to each other comprising means separating the rear portionof said lower spring leaf at a distance from said upper spring leaf whenthe vehicle is in a relatively unladen condition; and said upper springleaf and said lower spring leaf being shaped and secured with respect toeach other, and said second camming surface transmitting to the rearportion of said upper spring leaf a portion of the structural load onthe suspension when the vehicle is more fully laden comprising meansreducing said last-mentioned distance and causing the forward upperportion of the upper spring leaf and said rear portion of the lowerspring leaf bear a portion of the structural load on the suspension whenthe vehicle is more fully laden; the forward portion of the upper springleaf and the portion of the lower spring leaf and the portion of thelower spring leaf between said bracket and axle being of a taper withincreasing thickness rearwardly from said bracket to said axle.
 2. Theapparatus in claim 1 wherein the distance separating the rear portion ofsaid lower leaf from the rear portion of said upper leaf is the same asthe distance separating the forward end o the upper leaf from theforward camming surface when the vehicle is relatively unladen.
 3. Theapparatus in claim 1 wherein the forward end of said upper leaf is bentover into a hooklike shape extending forwardly of said means securingthe forward end of the lower leaf on said bracket.
 4. The apparatus inclaim 1 and means for adjusting the forward or rearward translation ofsaid axle for precise positioning thereof with respect to means ofdriving the wheels placed on said axle.
 5. The device of claim 1 whereina second axle is disposed rearwardly of said driven axle is disposedrearwardly of said driven axle and a like second suspension is providedfor said second axle; a walking beam journaled adjacent the centerthereof to said frame; said second camming surfaces comprising the endportions of said walking beam and including rubber members verticallyspaced below and secured to said end portions of said walking beam; therear portions of each of said upper and lower spring leaves positionedin said space defined between the end portions of said walking beam andthe associated rubber members whereby said rubber members provide alimit against downward motion of each said spring leaf rear portions. 6.The apparatus of claim 1 wherein said means securing the forward end ofthe lower spring leaf has a rubber bushing upon which said forward endis journaled.
 7. The device of claim 1 wherein a second axle is disposedrearwardly of said driven axle and a like second suspension is providedfor said second axle; a walking beam journaled adjacent the centerthereof to said frame; said camming surfaces comprising the end portionsof said walking beam, and said walking beam being relatively rigidcompared to said spring leaves.
 8. The device of claim 1 wherein saidmeans securing the forward end of said lower spring leaf includes meansjournaling said last-mentioned spring leaf to said bracket.
 9. Thedevice of claim 1 wherein a second axle is disposed rearwardly of saiddriven axle and a like second suspension is provided for said secondaxle; a walking beam journaled adjacent the center thereof to saidframe; said second camming surfaces comprising the end portions of saidwalking beam, and saiD walking beam having a spring rate of the sameorder of magnitude with respect to said spring leaves.
 10. The apparatusof claim 1 wherein the forward end of said lower spring leaf comprises afirst arm and the rear portion of said lower spring leaf comprises asecond arm, the spring rate in the first-mentioned arm being differentfrom the spring rate in the second mentioned arm.
 11. The apparatus ofclaim 1 including a longitudinally extending walking beam journaled atthe center thereof to said frame rearwardly of said driven axle, saidsecond camming surface being fixed to the forward end of said walkingbeam; said driven axle being a forward driven axle; a rear driven axleconstituting, together with said forward axle, a second upper taperedspring leaf having a thickness along a substantial length thereof atleast 30 percent greater than the thickness along another substantiallength thereof; a second lower tapered spring leaf having a thicknessalong a substantial length thereof at least 30 percent greater than thethickness along another substantial length thereof; means securing saidsecond upper spring leaf and said second lower spring leaf to said rearaxle near the centers of said second upper and lower spring leaves; anaft bracket attached to the frame forwardly of said rear axle; a flangeon said aft bracket; a camming surface on the underside of said flangeon said aft bracket; said second upper spring leaf and said second lowerspring leaf being shaped and secured with respect to each othercomprising means separating the forward portion of said second upperspring leaf at a distance from said camming surface on said aft bracketwhen said vehicle is relatively unladen; means securing the forward endof said second lower spring leaf on said aft bracket; a camming surfaceon the aft end of said walking beam and in contact with the rear portionof said second upper spring leaf; said second upper spring leaf and saidsecond lower spring leaf being shaped and secured with respect to eachother comprising means separating the rear portion of said second lowerspring leaf at a distance from said second upper spring leaf when thevehicle is in a relatively unladen condition; and said second upperspring leaf and said second lower spring leaf being shaped and securedwith respect to each other, and said camming surface on the aft end ofsaid walking beam transmitting to the rear portion of said second upperspring leaf a portion of the structural load on the suspension when thevehicle is more fully laden comprising means reducing saidlast-mentioned distance and causing the forward upper portion of thesecond upper spring leaf and said rear portion of the second upperspring leaf and said rear portion of the second lower spring leaf tobear a portion of the structural load on the suspension when the vehicleis more fully laden; the forward portion of the second upper spring leafand the portion of the second lower spring leaf between said aft bracketand said rear axle being of a taper with increasing thickness rearwardlyfrom said aft bracket to said rear axle.
 12. The apparatus of claim 1and means continuously and smoothly increasing the share of structuralload on said rear portion of said lower spring leaf placed by thevehicle on the suspension as the vehicle is more fully laden.
 13. Theapparatus of claim 1 and said forward portion of said upper spring leafbeing shaped and positioned with respect to said camming surface andsaid flange of said forward bracket comprising means preventing saidforward portion of said upper spring leaf from bearing a structural loaduntil a predetermined threshold of load is placed on the vehicle abovean unladen condition.